1. Field of the Invention
This invention relates generally to methods and apparatus for treating polychlorinated biphenyl contaminated sludge, such as the sand, mud, or the like, forming the bottoms of PCB contaminated lakes and streams.
2. Background Art
Since 1978 the manufacture of polychlorinated biphenyls (PCBs) has been banned in the United States. These chemicals have been widely used in the past in transformers, carbonless carbon paper, hydraulic pumps, caulking compounds, inks, paints and insect sprays. A tremendous amount of these chemicals, suspected of causing cancer and birth defects, have been dumped over a number of years in an entirely reckless fashion. Commonly these chemicals were dumped in lakes, streams and waterways where they eventually collected in the bottom material in considerable concentrations.
Because of the method of dumping these chemicals, a tremendous mass of material has been contaminated with these chemicals. In the past, bottom soils or the like contaminated with these fluids have been treated by attempting to burn or by burying them. Because of the nature of the materials in which the PCB contamination is often found, burning is extremely difficult and burying is often only a stop gap measure.
It has been recognized that thermal decomposition of polychlorinated organic compounds is possible despite the very high degree of thermal stability of these compounds. U.S. Pat. No. 4,140,066 discloses a method of decomposing PCB's by exposure to heat in a combustion chamber which operates with extremely intense turbulance and pulsation under temperatures as low as 850.degree. C. and with residence times as short as 0.1 second. However, the patent provides no method or apparatus for dealing with the problem of the treatment of mountainous amounts of contaminated, wet material having a relatively low heating value. Thus while the method set forth in the '066 patent may be highly useful in eliminating PCB containing compounds in relatively small volumes, the process is not particularly helpful in dealing with contaminations on the order of tons in the form of residues in sludge.
A variety of techniques for incinerating waste material are known. The following U.S. Pat. Nos. are exemplary: 4,245,570; 3,858,534; 3,829,558; 3,812,794; 3,716,339; and 3,511,194.